FIG. 2 shows an example of conventional resolution conversion (RC) process in the most simple form. In FIG. 2, a RC unit 103 converts a resolution of an original image 10 and outputs an image with a target size, i.e. a target size image 20.
In the conventional art, the procedure performed by the RC unit 103 aims to obtain a desired image size as quickly as possible. Accordingly, one step RC procedure is used. In other words, the input image is directly downsized to the target size.
An example of such one step RC procedure is described in Japanese Patent Application Laid-open 2001-160947, Sections 0027 and FIGS. 4 and 7, in which detail procedure for producing a thumbnail image from a typical size image by reducing a resolution of the original image. In this example of the one step RC procedure, a thumbnail image is produced from an original image by reducing the horizontal and vertical size to ¼. More specifically, one pixel is sampled in every four pixels in the horizontal direction, and one line is sampled in every four lines in the vertical direction.